Cypress Semiconductor CY7C68301C Manual de usuario descargar pdf (Pagina 20)

CY7C68300C, CY7C68301C

CY7C68320C, CY7C68321C

Document Number: 001-05809 Rev. *K Page 20 of 44

Fused Memory Data

When no EEPROM is detected at startup, the AT2LP

enumerates with the VID/PID/DID values that are stored in the

fused memory space. These values can be programmed into the

AT2LP during chip manufacturing for high volume applications to

avoid the need for an external EEPROM in some designs.

Contact your local Cypress Semiconductor sales office for more

information on this feature.

If no factory programming has been done, the values returned

from the fused memory space would all be 0x00, which is not a

valid mode of operation. In this case the chip uses the

manufacturing mode and return the default descriptors (VID/PID

of 0x4B4/0x6830). An EEPROM must be used with designs that

do not use factory-programmed chips to identify the device as

your company’s product.

Normal Mass Storage Mode

In Normal Mass Storage Mode, the chip behaves as a USB 2.0

to ATA/ATAPI Bridge. This includes all typical USB device states

such as powered and configured. The USB descriptors are

returned according to the values stored in the external EEPROM

or fused memory space. A unique serial number is required for

Mass Storage Class Bulk-Only Transport compliance, which is

one reason why an EEPROM or factory-programmed part is

needed.

Board Manufacturing Test Mode

In Board Manufacturing Test Mode the AT2LP behaves as a

USB 2.0 device but the ATA/ATAPI interface is not fully active.

This mode must not be used for mass storage operation in a

finished design. In this mode, the AT2LP enable reading from

and writing to the EEPROM, and for board level testing, through

vendor- specific ATAPI commands utilizing the CBW Command

Block as described in the USB Mass Storage Class Bulk-Only

Transport Specification. There is a vendor-specific ATAPI

command for EEPROM accesses (CfgCB) and one for board

level testing (MfgCB), as described in the following sections.

There is a convenient method available for starting the AT2LP in

Board Manufacturing Test Mode to enable reprogramming of

EEPROMs without a mass storage device attached. If the ATA

Reset (ARESET#) line is LOW on power up, the AT2LP enters

Board Manufacturing Test Mode. It is recommended that a

10k resistor be used to pull ARESET# to LOW. An easy way to

pull the ARESET# line LOW is to short pins 1 and 3 on the 40-pin

ATA connector with a 10k resistor, that ties the ARESET# line to

the required pull down on DD7.

CfgCB

The cfg_load and cfg_read vendor-specific commands are

passed down through the bulk pipe in the CBWCB portion of the

CBW. The format of this CfgCB is shown as follows. Byte 0 is a

vendor-specific command designator whose value is

configurable and set in the configuration data (address 0x04).

Byte 1 must be set to 0x26 to identify it as a CfgCB command.

Byte2 is reserved and must be set to zero. Byte 3 is used to

determine the memory source to write/read. For the AT2LP, this

byte must be set to 0x02, indicating the EEPROM is present.

Bytes 4 and 5 are used to determine the start address, which

must always be 0x0000. Bytes 6 through 15 are reserved and

must be set to zero.

The data transferred to the EEPROM must be in the format

specified in Table 11 on page 23 of this data sheet. Maximum

data transfer size is 255 bytes.

The data transfer length is determined by the CBW Data Transfer

Length specified in bytes 8 through 11

(dCBWDataTransferLength) of the CBW (refer to Table 7). The

type/direction of the command is determined by the direction bit

specified in byte 12, bit 7 (bmCBWFlags) of the CBW (refer to

Table 7).

Table 7. Command Block Wrapper

Bits

Offset 7 6 5 4 3 2 1 0

0–3 DCBWSignature

4–7 dCBWTag

8–11 (08h–0Bh) dCBWDataTransferLength

12 (0Ch) bwCBWFLAGS

Dir Obsolete Reserved (0)

13 (0Dh) Reserved (0) bCBWLUN

14 (0Eh) Reserved (0) bCBWCBLength

15–30 (0Fh1Eh) CBWCB (CfgCB or MfgCB)

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 43 44

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